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HURRICANE GERT DISCUSSION NUMBER  18
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT WED SEP 15 1999

...COR TO WRONG TEXT...

VISIBLE SATELLITE IMAGES SHOW THAT GERT HAS AN IMPRESSIVE CLOUD
PATTERN WITH AN EYE EMBEDDED WITHIN A ROUND CENTRAL DENSE OVERCAST
AND NUMEROUS BANDING FEATURES. THE OUTFLOW IS EXCELLENT IN ALL
QUADRANTS.  T-NUMBERS FROM TAFB AND SAB ARE 6.5 AND 7.0 ON THE
DVORAK SCALE.  THIS MAKES GERT A VERY STRONG CATEGORY FOUR HURRICANE
ON THE SAFFIR/SIMPSON SCALE.  HURRICANES NORMALLY DO NOT KEEP SUCH
AN INTENSITY FOR A LONG TIME.  HENCE...FLUCTUATIONS IN INTENSITY ARE
EXPECTED DURING THE NEXT 3 DAYS.
 
INITIAL MOTION IS 275/11. THE HURRICANE IS MOVING WESTWARD AROUND
THE PERIPHERY OF A STRONG SUBTROPICAL RIDGE WHICH IS CONTROLLING THE
MOTION AT THIS TIME.  LATER...GERT WILL BE APPROACHING THE UPPER-
LOW PARTIALLY GENERATED BY THE OUTFLOW OF FLOYD.  THIS FEATURE...
WHICH IS CLEARLY OBSERVED ON WATER VAPOR IMAGES WILL PROBABLY FORCE
THE HURRICANE ON A MORE NORTHWESTERLY TRACK...AWAY FROM THE LEEWARD
ISLANDS.  THEREAFTER...A BROAD TROUGH WHICH IS FORECAST TO PERSIST
OVER THE WESTERN ATLANTIC WILL STEER THE HURRICANE ON A MORE
NORTHERLY TRACK.   THIS IS THE SOLUTION PROVIDED BY MOST OF THE
TRACK AND LONG RANGE GLOBAL MODELS.

A NOAA GULFSTREAM PLANE WILL SAMPLE THE ENVIRONMENT OF THE HURRICANE
TONIGHT AND AN AIR FORCE PLANE WILL PENETRATE THE EYE EARLY
THURSDAY.  
 
AVILA
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     15/2100Z 17.6N  50.7W   130 KTS
12HR VT     16/0600Z 17.8N  52.4W   130 KTS
24HR VT     16/1800Z 18.5N  54.5W   125 KTS
36HR VT     17/0600Z 19.2N  56.0W   125 KTS
48HR VT     17/1800Z 20.5N  58.0W   125 KTS
72HR VT     18/1800Z 23.5N  61.0W   125 KTS
 
 
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